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Arctic and Antarctic

Polar Amplification

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Guest commentary by Cecilia Bitz, University of Washington

“Polar amplification” usually refers to greater climate change near the pole compared to the rest of the hemisphere or globe in response to a change in global climate forcing, such as the concentration of greenhouse gases (GHGs) or solar output (see e.g. Moritz et al 2002). Polar amplification is thought to result primarily from positive feedbacks from the retreat of ice and snow. There are a host of other lesser reasons that are associated with the atmospheric temperature profile at the poles, temperature dependence of global feedbacks, moisture transport, etc. Observations and models indicate that the equilibrium temperature change poleward of 70N or 70S can be a factor of two or more greater than the global average. [Read more…] about Polar Amplification

Methane hydrates and global warming

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There is an enormous amount of methane (CH4) on earth frozen into a type of ice called methane hydrate. Hydrates can form with almost any gas and consist of a ‘cage’ of water molecules surrounding the gas. (The term ‘clathrate’ more generally describes solids consisting of gases are trapped within any kind of cage while hydrate is the specific term for when the cage is made of water molecules). There are CO2 hydrates on Mars, while on Earth most of the hydrates are filled with methane. Most of these are in sediments of the ocean, but some are associated with permafrost soils.

Methane hydrates would seem intuitively to be the most precarious of things. Methane hydrate melts if it gets too warm, and it floats in water. Methane is a powerful greenhouse gas, and it degrades to CO2, another greenhouse gas which accumulates in the atmosphere just as fossil fuel CO2 does. And there is a lot of it, possibly more than the traditional fossil fuel deposits. Conceivably, climate changes could affect these deposits. So what do we know of the disaster-movie potential of the methane hydrates?

[Read more…] about Methane hydrates and global warming

650,000 years of greenhouse gas concentrations

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Translations: (Français)

The latest results from the EPICA core in Antarctica have just been published this week in Science (Siegenthaler et al. and Spahni et al.). This ice core extended the record of Antarctic climate back to maybe 800,000 years, and the first 650,000 years of ice have now been analysed for greenhouse gas concentrations saved in tiny bubbles. The records for CO2, CH4 and N2O both confirm the Vostok records that have been available for a few years now, and extend them over another 4 glacial-interglacial cycles. This is a landmark result and a strong testament to the almost heroic efforts in the field to bring back these samples from over 3km deep in the Antarctica ice. So what do these new data tell us, and where might they lead? [Read more…] about 650,000 years of greenhouse gas concentrations

Saltier or not?

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Translations: (Français)

In a recent (of Sept. 16, 2005) publication in Science, Hatun et al. find that record-high salinities have been observed over the past decade in the region where water from the Atlantic flows into the northern oceans. They combine an analysis of observations with simulations using an ocean model, concluding that the salinity of the inflow to the northern oceans is controlled by ocean dynamics and the circulation in the sub-polar gyre. The observations by Hatun et al. may suggest that at the moment the warm and salty waters from the south are especially warm and salty.

In another publication paper in Science from June 17th 2005, on the other hand, Curry & Mauritzen conclude that as a whole the northern North Atlantic has become significantly fresher (less salty) in recent decades. The latter study was based entirely on observations (hydrographic data between Labrador and Europe in the past 50 years). The recent evidence for salinification provided by Hatun et al. has been interpreted by some as being inconsistent with the evidence for high-latitude North Atlantic freshening found in previous reports. So what is really happening? Is the salinity increasing or decreasing? And can the two recent Science studies be consistent with each other?

[Read more…] about Saltier or not?

2005 Record Arctic Ozone Loss

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You read it here first!


Update (09/05/05): Markus Rex was kind enough to send us the full figure from which Nature made their thumbnail, and which is a little clearer. He also cautions that the 2005 numbers are still preliminary, however there is a clear trend towards increasing potential for Arctic ozone loss, which is realised or not depending on the vagaries of each individual winter.

Retreating Glacier Fronts on the Antarctic Peninsula over the Past Half-Century

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Translations: (Français)

Guest commentary by David Vaughan

The recent retreat of ice shelves on the Antarctic Peninsula has been widely attributed to warming atmospheric temperatures. There is, however, little published work describing the response of glacier margin positions to this regional climate change. In the paper Retreating Glacier Fronts on the Antarctic Peninsula over the Past Half-Century published this week in Science, we presented new data describing trends in 244 marine glacier fronts on the Antarctic Peninsula over the last 50 years. The data come from matching archives of over 2000 aerial photographs of the Antarctic Peninsula to satellite images, and represent about three years of work by Alison Cook. The work was carried out at British Antarctic Survey, but was funded by the US Geological Survey, as part of a larger programme to map change in the coastline of all Antarctica.

[Read more…] about Retreating Glacier Fronts on the Antarctic Peninsula over the Past Half-Century

Will spring 2005 be a bad one for Arctic ozone?

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Translations: (Français)

Guest Commentary by Drew Shindell (NASA GISS)

The current winter and early spring have been extremely cold in the Arctic stratosphere, leading to the potential for substantial ozone depletion there. This has been alluded to recently in the press (Sitnews, Seattle Post Intelligencer), but what’s the likely outcome, and why is it happening?

[Read more…] about Will spring 2005 be a bad one for Arctic ozone?

Senator Inhofe on Climate Change

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by Michael Mann, Stefan Rahmstorf, Gavin Schmidt, Eric Steig, and William Connolley

Senator James Inhofe (R) of Oklahoma recently provided us with an update of his views on the issue of climate change in a speech given on the opening senate session, January 4, 2005. His speech opened with the statement:

As I said on the Senate floor on July 28, 2003, “much of the debate over global warming is predicated on fear, rather than science.” I called the threat of catastrophic global warming the “greatest hoax ever perpetrated on the American people,” a statement that, to put it mildly, was not viewed kindly by environmental extremists and their elitist organizations.

Cutting through much of his polemic, Inhofe’s speech contains three lines of scientific argument which, according to him, provide “compelling new scientific evidence” that anthropogenic global warming is not threatening. We here submit his statements to scrutiny.
[Read more…] about Senator Inhofe on Climate Change

Michael Crichton’s State of Confusion

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Translations: (Français)

In a departure from normal practice on this site, this post is a commentary on a piece of out-and-out fiction (unlike most of the other posts which deal with a more subtle kind). Michael Crichton’s new novel “State of Fear” is about a self-important NGO hyping the science of the global warming to further the ends of evil eco-terrorists. The inevitable conclusion of the book is that global warming is a non-problem. A lesson for our times maybe? Unfortunately, I think not.

[Read more…] about Michael Crichton’s State of Confusion

The Arctic Climate Impact Assessment

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In early November 2004 the results of the Arctic Climate Impact Assessment (ACIA) were published, a uniquely detailed regional study compiled by 300 scientists over 3 years. The study describes the ongoing climate change in the Arctic and its consequences: rising temperatures, loss of sea ice, unprecedented melting of the Greenland ice sheet, and many impacts on ecosystems, animals and people. The ACIA is the first comprehensively researched, fully referenced, and independently reviewed evaluation of arctic climate change and its impacts for the region and for the world.

Sadly, in recent years we have become accustomed to a ritual in which the publication of each new result on anthropogenic climate change is greeted by a flurry of activity from industry-funded lobby groups, think tanks and PR professionals, who try to discredit the science and confuse the public about global warming.

[Read more…] about The Arctic Climate Impact Assessment